1. Field of the Invention
The present invention, generally, relates to print hammer mechanisms and, more particularly, to a passive lubrication system for use with the operating elements of print hammer mechanisms.
It has been found that, while use of sintered blocks, pins and other structures to provide reservoirs for lubricants permits a dramatic increase in the performance life of high speed print hammers, the lack of control over lubricant flow limits the scope of use for that form of lubrication system.
2. Description of the Prior Art
The prior art is rich with teachings of structures that concern lubricating bearing surfaces between metal parts having relative movement. However, special circumstances do not always lend themselves to these well known prior structures.
For example, with the advent of high speed printers as output devices for data processing equipment, problems have included the prevention of excessive wear between moving parts. Solutions that have been entirely satisfactory in one situation have proven to be entirely unsatisfactory in another, and this is especially true as the operating speeds of such high speed printers have increased to mind boggeling rates.
U.S. Pat. No. 4,756,246 to Kotasek et al. is assigned to the same Assignee as the present invention and describes the type of structural improvement that offers the advantage of increased operating life for these high speed printer mechanisms. Notwithstanding such advantage, however, the present invention permits a still further increase in the operating life of the print hammer modules because of advantages that accrue from the control over lubricant flow, which is obtained from the structure of the invention.
While this prior U.S. patent discloses some of the problems associated with the development of such high speed printers, it and none of the known prior patents and publications disclose or even suggest a solution such as that provided by the present invention. It is known now that the extremely high speeds at which these printer elements operate develop pressures on lubricant materials that are alternately positive and negative.
The use of sintered material structures as lubricant reservoirs and such material, as well as softer wick material, to convey the lubricant from the reservoirs to the area of need has become well known in the industry. However, none of these previously known arrangements permit control over the lubricant flow, and therefore, there has been no control over the rate of lubricant depletion.